The present invention generally relates to feed-thru capacitors of the type used in implantable medical devices such as heart pacemakers, defibrillators, and neurostimulators. More specifically, the instant invention relates to a multi-leaded feed-thru assembly combining a capacitive device and additional semi-conductive devices for use in implantable medical devices. Still further, the present invention relates to a multi-leaded feed-thru assembly which integrates both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter device to provide filtration of electromagnetic interference (EMI).
Conventional feed-thru capacitive devices are known. In particular, ceramic capacitor feed-thru assemblies for use in implantable medical devices are known. With the continued miniaturization of electric devices and the desire for less invasive medical procedures, smaller multi-functional devices have become needed to increase the capabilities of implantable medical devices such as pacemakers while maintaining or even reducing their size and simultaneously increasing their reliability.
U.S. Pat. No. 5,735,884, issued to Thompson et al. and incorporated fully herein by reference, discloses a filtering feed-thru assembly for implantable medical devices. The ""884 assembly, however, provides poor EMI filter performance due to the use of chip capacitors. While useful for its purpose, the absolute requirement for reliability of these implantable devices mandates that the feed-thru filter must be capable of filtering (i.e., reflecting or absorbing and decoupling) substantially all EMI to prevent damage to the device""s internal circuitry. Failure of the implantable device could result in the loss of function of the medical device and possibly the loss of the patient""s life.
U.S. Pat. Nos. 4,424,551 and 5,333,095, issued to Stevenson et al. and incorporated fully herein by reference, also disclose feed-thru filtering capacitive assemblies for use in medical devices. Neither of these assemblies, however, provides for the attachment of semiconductor or passive component devices to such filtering feed-thru devices. This results in an increase in medical device size due to the requirement for downstream assembly of such additional components into the internal circuitry of such a device, in addition to the associated increase in costs. Additionally, neither the ""551 nor the ""095 assembly provides for suppression of transient voltages at their point of entry (i.e., the end of the electrically conductive leads external to the implantable device).
It is, therefore, desirable to provide a multi-leaded feed-thru assembly capable of reliably and thoroughly filtering EMI, as well as, suppressing transient voltages at their point of entry into the implantable medical device and integrating both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter.
The present invention recognizes and addresses various of the foregoing limitations and drawbacks, and others, concerning the filtration of electromagnetic interference, the suppression of transient voltages, and the integration of additional electronic components into a single assembly for implantable medical devices resulting in the reduction in size and increase in reliability of the medical device. Therefore, the present invention provides a new multi-leaded filtering feed-thru assembly for filtering EMI, such as may be generated by cellular telephones, and suppressing transient voltages, such as may be generated by a defibrillator, as well as allowing for the integration of additional electronic components into the assembly.
It is a principle object of the subject invention to provide a filtering feed-thru capacitive device. More particularly, it is an object of the present invention to provide a filtering feed-thru capacitive assembly capable of inclusion in an implantable medical device.
Another more particular object of the present invention is to provide a filtering feed-thru assembly capable of filtering EMI as may be experienced by an implanted medical device. In such context, it is a still further object of the present invention to provide a filtering feed-thru assembly capable of suppressing transient voltages as may be experienced by an implanted medical device.
It is a further general object of the present invention to provide a filtering feed-thru assembly capable of integration with both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof. In such context, it is a still further object to provide a filtering feed-thru assembly comprising a discoidal capacitive filter.
It is a more specific object of the present invention to provide a filtering feed-thru assembly for an implantable medical device, capable of filtering electromagnetic interference from any external signals entering the device, suppressing any transient voltages at their entry point into the device, and capable of integration with both multi-element semiconductor and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter.
Additional objects and advantages of the invention are set forth in, or will be apparent to those of ordinary skill in the art from, the detailed description as follows. Also, it should be further appreciated that modifications and variations to the specifically illustrated and discussed features and materials hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitutions of equivalent means, features, and/or materials for those shown or discussed, and the functional or positional reversal of various parts, features, or the like.
Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of this invention, may include various combinations or configurations of presently disclosed features, elements, or their equivalents (including combinations of features or configurations thereof not expressly shown in the figures or stated in the detailed description).
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention.
In one exemplary embodiment of the present invention the assembly comprises a feed-thru filter for a pacemaker or other implantable medical device. Such assembly may have a header, a support plate, with a flange around its outer perimeter for attachment in an opening in the housing of the implantable device. Such attachment can be achieved through any known means but is typically completed by welding or brazing and is preferably a hermetic sealing of the assembly within such opening in the device.
Within such header may be a single opening or set of openings through which extend multiple electrically conductive terminal pins. A first end of each of such pins remains external to the implantable medical device when such assembly is connected thereto. Preferably, the opening or set of openings in such header through which such pins pass is hermetically sealed. Within the opening or within each opening in a set of openings may be an electrically insulative support. Such supports, while aiding in sealing the opening or set of openings, may maintain the pins within the opening or set of openings and electrically insulate them from portions of the circuitry of such assembly and such medical device.
A discoidal capacitor may be bonded to such header by a conductive polyamide. Such discoidal capacitor may have a second set of openings formed therethrough. Such openings in the capacitor may align with the opening or set of openings through such header when the two are bonded together. This may allow for electrical connection between such discoidal capacitor and such electrically conductive terminal pins.
Within such discoidal capacitor may be a first set of electrode plates arranged to be suitable for parallel connections with such pins and a second set of electrode plates arranged to be suitable for series connections with such pins. Such parallel connections with the pins allow-for the filtering of a majority of any electromagnetic interference which may be experienced by such medical devices. Similarly, such series connections with the pins allow for suppression of transient voltage spikes as may be experienced by such implantable devices during defibrillation. In particular, direct current (DC) is reflected or blocked and alternating current (AC) is absorbed and decoupled by the series capacitive electrode plates.
On the opposing side of such discoidal capacitor from such header, electrically conductive patterns may be disposed for further connection to additional electronic component elements. Such patterns may also provide for connection to the internal circuitry of such medical device. This may be achieved through either the use of wire bondable pads integrated into such patterns or a second set of terminal pins connected to such discoidal capacitor. In the later instance, the first set of such terminal pins may be used for suppressing transient voltages while the second set may be utilized to filter EMI or vise versa.
Should such patterns be used for connection to an additional electrical component, such component may be a multi-element semiconductor and a passive component device, or a multi-element combination thereof. For example, such electrical component may be a semiconductor attached to such discoidal capacitor by solder reflow, a multi-element passive component attached by epoxy bonding and conductive polyamide, or a thick film resistor or inductor attached by firing.
One of ordinary skill in the art would recognize that any combination of additional electronic component, such discoidal capacitor, and connection type to the internal circuitry of such implantable devices is possible. Additionally, such terminal pins may be located in-line or on a bolt circle and such insulative supports may constitute either a single multi-hole support or individual supportive elements. Finally, such header may either provide only a supportive plate for the remainder of the assembly or may constitute a canister to contain the entire assembly.